In oil well drilling and production operations in both land and subsea locations, oil, mud, and hydraulic fluids are normally transmitted through an annulus formed between successive generally concentric casings. In particular, such fluids are transmitted through an annulus defined by an oil well casing and a tubing string suspended within the casing. Quite often, these fluids are transmitted under very high pressure with flow directions through the annulus being in opposite directions during various operations at the oil well.
It has long been a problem to effectively control the flow of these high pressure fluids through the annulus created by the concentric conduits. Various solutions to this problem are found in the prior art. For example, one solution has been to seal the annulus by sealing elements within the casing to prevent fluid passage through the annulus. An access port into the annulus is then provided through the sealing elements. Fluid flow into or out of the sealed annulus is controlled by means of a valve external to the sealing elements at the access port. Such an arrangement presents many problems, especially where the casing is not readily available, as is the case in subsea oil well drilling and production operations where the casing head may be on the seafloor hundreds of feet below a drilling platform from which drilling and production operations are being conducted. Additionally, with this type of arrangement, the fluid flow within the annulus is not controlled from within the annulus itself, but must be directed through a valve external of the annulus. This requires additional piping and controls, which are undesirable in subsea oil well drilling and production operations. It is particularly essential to be able to easily and effectively seal off the annulus in such subsea operations since other fluid control means embodied in blow-out prevention equipment, or a production control trees, for example, must be periodically removed during the course of the drilling and production operations.
Another solution found in the prior art, and described by U.S. Pat. No. 3,360,048, issued to this inventor on Dec. 26, 1967, is to suspend an annulus valve from a tubing hanger landed in sealing relation within an oil well casing. The annulus valve divides the tubing-casing annulus into two portions, and passages are provided between the two portions. A closure means is provided to seal the opening between the portions of the annulus, and thus to prevent fluid flow therethrough. Such closure means is operated by wire line tools positioned within the hanger bore. However, a problem with such an arrangement is that a tool adapted to operate the closure means necessarily has to be inserted into the hanger bore. Additionally, such a valve is a discrete component in the oil well equipment string, which utilizes space in the string into which another tool or apparatus could otherwise be inserted.
As hydraulic fluid is frequently utilized in oil wells to control various devices within the well, it would be attractive to eliminate the dependence on wire line tools or other such devices for controlling an annulus valve, and to utilize instead the hydraulic fluid to control the valve. Such fluid is frequently available from tubing mandrels attached to production trees. It would be also attractive to combine an annulus valve with another component in an oil well, such as a tubing hanger.
Accordingly, it is the principal object of the present invention to control fluid flow through an annulus formed between an oil well casing and a tubing string suspended therein in a manner not requiring the use of separate control elements external to the casing or positioned within the tubing bore.
It is another object of the present invention to control fluid flow through a tubing-casing annulus in an oil well installation through the use of hydraulic control fluid.
It is an additional object of the present invention to integrate an annulus valve into a tubing hanger positioned within the casing.
It is still another object of the present invention to allow actuation of an annulus valve integrated within a tubing hanger by the insertion of a tubing mandrel into the tubing hanger.
It is another object of the present invention to provide an annulus valve which may be easily inserted and removed from an oil installation.
It is also an object of the present invention to control fluid flow through a tubing-casing annulus formed between a casing and an inner tubing by way of an apparatus landed within the casing in sealing relation and dividing the annulus into an upper and lower portion, where the apparatus is connected to the tubing and has an apparatus bore communicating with the tubing bore and passages communicating between the upper and lower portions of the annulus, and also has hydraulically-activated means, communicating with the tubing bore, for opening the passages to fluid flow between the annulus portions.
It is the final object of the present invention to provide an annulus valve capable of equalizing fluid pressures exerted on opposite sides of the moving parts of the valve to balance their effects on opening and closing operations under high fluid pressures in the well.